Structure and intermolecular excitations of β-N2 at 400 MPa and 55 K

Powell, B. M.; Dolling, G.; Nieman, H.

doi:10.1063/1.445878

Cited by 39 publications

(18 citation statements)

References 28 publications

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“…Three elastic constants, for P-N2 at 37 K, could be deduced from slopes of their dispersion curves and are shown in Table 1. Agreement is reasonable with the present 47.5 K results when extrapolated at 37 K. Powell et al (42) used this technique to determine three elastic constants e l l , c~~, and cj4 for P-N,, at 55 K and 400 MPa, and they appear to increase dramatically with pressure. ( 6 ) Phase transformation mechanism…”

Section: Discussion (A) Elastic Constantssupporting

confidence: 70%

Brillouin scattering near the α–β phase transitions of N₂ and CO

Askarpour¹,

Klefte²,

Clouter³

1988

Can. J. Chem.

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The technique of high resolution Brillouin spectroscopy has been used to determine the adiabatic elastic constants of single crystals of P-N2 and P-CO as a function of temperature, in an effort to study the a-P phase transition. For all elastic constants, there is an increase of approximately 1 %/K on cooling and there is no evidence of further mode softening, even within 0.5 K of the phase transition. Three large single crystals of a-CO were grown. The orientations were determined, by Laue X-ray diffraction, and correlated to the orientations of the parent P-crystals. The P-phase hexagonal basal planes appear to transform to planes of the form {I 1 0 ) in the a-phase cubic structure.V. ASKARPOUR, H. KIEFTE et M. J. CLOUTER. Can. J. Chem. 66, 541 (1988). Dans le but d'etudier la transition de phase a-P, on a utilise la technique de la spectroscopie de Brillouin 2 haute rCsolution pour determiner les constantes Clastiques adiabatiques de cristaux uniques de P-N, et P-CO en fonction de la temperature. Pour toutes les constantes Clastiques, on observe une augmentation d'environ 1%/K lorsqu'on refroidit; de plus, on ne dCtecte pas d'autre assouplissement de mode, m&me a 0,5 K de la transition de phase. On a fait croYtre trois gros cristaux uniques d'a-CO. On en a determine les orientations par diffraction des rayons-X selon Laue et on a Ctabli un corrClation avec les orientations des cristaux p apparent&. I1 semble que les plans hexagonaux de base de la phase P se transforment en plans de la forme {I I 0 ) lorsqu'on passe B la structure cubique de la phase a .[Traduit par la revue] Introduction Brillouin spectroscopy is a very effective technique for probing the dynamical behaviour of phonons in crystals and lattice instability associated with phase transitions. In particular, it allows for accurate determination of elastic constants in single crystals. The present work constitutes an attempt to use Brillouin spectroscopy (and Laue X-ray diffraction) to study very simple phase transitions in diatomic molecular solids, namely, the ol-P transitions in solids N2 and CO. This represents a continuation of previous Brillouin scattering experiments on single crystals of P-N2 (1) and P-CO (2) very close to their triple points.

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Section: Discussion (A) Elastic Constantssupporting

confidence: 70%

Brillouin scattering near the α–β phase transitions of N₂ and CO

Askarpour¹,

Klefte²,

Clouter³

1988

Can. J. Chem.

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“…This exceed considerably the Debye frequency 1.0×10 -12 sec -1 . No distinct libration modes were detected in β-N 2 in inelastic neutron scattering experiments, and even the observed translational acoustic phonons were broadened considerably due to the translation-orientation interaction, excluding the case of the smallest wave vectors [10].…”

Section: ): ()-Smoothed Values (----)-Measurement Under Saturated Va-mentioning

confidence: 99%

Isochoric thermal conductivity of solid nitrogen

Konstantinov

Manzheliı̆

Revyakin

et al. 2005

Low Temperature Physics

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The isochoric thermal conductivity of solid nitrogen has been investigated on four samples of different densities in the temperature interval from 20 K to the onset of melting.In α-N 2 the isochoric thermal conductivity exhibits a dependence weaker than Λ∝1/T; in β-N 2 it increases slightly with temperature. The experimental results are discussed within a model in which the heat is transported by low-frequency phonons or by «diffusive» modes above the mobility boundary. The growth of the thermal conductivity in β-N 2 is attributed to the decreasing «rotational» component of the total thermal resistance, which occurs as the rotational correlations between the neighboring molecules become weaker.

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“…If, in addition, the anisotropic orientational interactions are weak, the disorder closely approximates free molecular rotation. Examples are H 2 [10], CD 4 [11] and fl-N 2 [12].…”

Section: Introductionmentioning

confidence: 99%

Collective excitations in an orientationally frustrated solid; neutron scattering and computer simulation studies of SF₆

et al. 1986

Self Cite

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Collective excitations in the orientationally disordered phase of SF 6 have been studied by inelastic neutron scattering and molecular dynamics simulation techniques. Experimental measurements to observe acoustic modes were made along the high symmetry directions at temperatures of 100K and 200 K. The excitations observed showed little evidence of discrete peaks but were all broad and overdamped. They showed little temperature dependence. The dynamical structure factors S(O, co) calculated from the simulation are in qualitative agreement with the observed spectra but quantitatively show discrepancies. For smaller wave vectors than those studied experimentally the calculations show the existence of well-defined, long wavelength acoustic phonons. The wave vector at which the transition occurs between propagating and overdamped excitations was found to be temperature dependent. The results are interpreted in terms of the concept of orientational frustration. Some difficulties in the application of molecular dynamical simulation to the calculation of dynamical correlation functions are discussed in an Appendix.

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Structure and intermolecular excitations of β-N2 at 400 MPa and 55 K

Cited by 39 publications

References 28 publications

Brillouin scattering near the α–β phase transitions of N₂ and CO

Brillouin scattering near the α–β phase transitions of N₂ and CO

Isochoric thermal conductivity of solid nitrogen

Collective excitations in an orientationally frustrated solid; neutron scattering and computer simulation studies of SF₆

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Structure and intermolecular excitations of β-N2 at 400 MPa and 55 K

Cited by 39 publications

References 28 publications

Brillouin scattering near the α–β phase transitions of N2 and CO

Brillouin scattering near the α–β phase transitions of N2 and CO

Isochoric thermal conductivity of solid nitrogen

Collective excitations in an orientationally frustrated solid; neutron scattering and computer simulation studies of SF6

Contact Info

Product

Resources

About

Brillouin scattering near the α–β phase transitions of N₂ and CO

Brillouin scattering near the α–β phase transitions of N₂ and CO

Collective excitations in an orientationally frustrated solid; neutron scattering and computer simulation studies of SF₆